This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled xe2x80x9cAPPARATUS AND METHOD FOR COMPENSATING RECEIVED SIGNAL STRENGTH INDICATOR ACCORDING TO TEMPERATURExe2x80x9d filed in the Korean Industrial Property Office on Dec. 20, 1999 and there duly assigned Serial No. 99-59246.
1. Field of the Invention
The present invention relates generally to an intermediate circular orbit satellite communication terminal, and in particular, to an apparatus and method for adjusting setting of the received signal strength indicator according to temperature changes in the terminal.
2. Description of the Related Art
Generally, a satellite communication terminal is serviced through a low earth orbit satellite. In most cases, however, such a communication terminal is typically used in a poor whether condition when compared with other normal radio terminals. Therefore, it is important for the satellite communication terminal to accurately measure the power level RSSI (received signal strength indication) of the received signals. This is because, for mode switching of the satellite communication terminal, the RSSI is transmitted to a satellite repeater through the low earth orbit satellite such so the satellite repeater controls the transmission power of a forward link. The RSSI is also used to estimate a timing offset by profiling the transmission power during the initial sync acquisition operation. Therefore, the RSSI detected by the satellite communication terminal affects the overall communication system.
Now, with reference to FIG. 1, a description will be made of a procedure for detecting the RSSI in the satellite communication terminal.
FIG. 1 illustrates the structure of an RSSI detector according to the prior art. Referring to FIG. 1, when a signal is received at the satellite communication terminal, the received signal is applied to an analog-to-digital (A/D) converter 111 after going through a normal demodulation process which includes a successive processing of low-noise amplification (LNA), filteration, and amplification.
The A/D converter 111 converts an input analog signal to a digital signal. A filter 113 filters the digital signal output from the A/D converter 111, and an average power detector 115 detects an average power of the filtered signal output from the filter 113. A dBm converter 117 then converts the average power detected by the average power detector 115 to a dBm value, and provides the converted dBm value to an RSSI mapper 119. Upon receiving the dBm value output from the dBm converter 117, the RSSI mapper 119 detects an RSSI matching the outputted dBm value and provides the detected RSSI to a subsequent demodulation stage.
In the above RSSI detection process, the received signal will be affected by the internal temperature and/or ambient temperature of the satellite communication terminal as the received signal travels through a low noise amplifier (LNA), a filter, and an amplifier. This is because the LNA, the filter and the amplifier components are very susceptible to the temperature. To solve this problem, it is necessary to use components that are not affected by the temperature. However, the implementation of such components will increase the manufacturing cost. Moreover, even when such components are used, it will be difficult to detect an accurate RSSI value.
It is, therefore, an object of the present invention to provide an apparatus and method for adjusting setting of the received signal strength indicator (RSSI) according to a temperature variation.
To achieve the above and other objects, there is provided an apparatus for compensating a received signal strength (RSSI) according to temperature variation. The average power detector detects the average power of a received signal. An RSSI compensation value detector detects the internal temperature of the RSSI compensation apparatus and obtains an appropriate RSSI compensation value according to the detected temperature. To this end, the RSSI detector detects an RSSI by adding the average power value to the RSSI compensation value.